Procedure and filter device for removal and/or destruction of organic substances in contaminated air

ABSTRACT

A procedure and a filter device ( 1 ) serving the purpose of removing and/or destruction organic substances in contaminated air. The filter device comprises at least one ventilator ( 12 ) for sending an air stream through a first chamber ( 14 ) with an opening, which is connected with a source for contaminated air; a second chamber ( 15 ) with a number of sheets ( 20 ) placed abeam the main direction of the air stream in order to make the air stream change direction at least one time; a third chamber ( 16 ) with a number of perforated tubes ( 22 ) which at least at one end are in open connection to a secondary air source; a fourth chamber with a number of lamps for radiating the air stream with a short-waved ultra-violet light and; a fifth chamber ( 17 ) with a volume, which gives the air stream a predetermined duration time in the chamber, and which has an opening, through which the purified air passes in order to be released to the surroundings. The filter device ( 1 ) is extremely efficient for purifying contaminated air from organic substances without using chemicals and physical filters, such as fat- and carbon filters, and it is hygienic and fireproof, since its interior sheets are not covered with organic materials. The releasing tubes and the ventilator are furthermore easy to clean.

This is a natural stage application of PCT/DK97100182 filed Apr. 23,1997.

TECHNICAL FIELD

The invention concerns a procedure for removal and/or destructions oforganic substances in contaminated air.

BACKGROUND ART

Organic substances in the form of vapours or particles are to a largeextend created as undesired secondary products in connection with manyproduction processes within the industry. As examples can be mentionedpreparation and use of lacquer and paint, cereal and feedstuff, metaland plastic, tar and asphalt, tanneries, incinerating plants, bio-gasplants, market gardens, agriculture and also large parts of the foodindustry.

Today severe demands are made to the hygienic and health conditionsregarding the work spots/sites as well as to the surrounding milieu. Theorganic substances mentioned are, however, more or less injurious tohealth, and furthermore many of them have a foul smell. It willtherefore normally not be allowed to leak air contaminated with suchorganic substances to the surroundings. Purification of the air musttake place before that.

This purification normally takes place by filtering he contaminated airin, for example, grease filters and carbon filters. Mechanical filtersof this type are, however, rather expensive in use, since they need tobe cleaned at short intervals and frequently have to be replaced.Furthermore, the filters cannot fulfill the high hygienic standard,which, for example, is required within the food industry, and to thiscan be added that filters, which, as an example, are filled with grease,must be considered as extremely flammable.

Furthermore, it is known technology to use ozone for removing especiallyfoul smell from air contaminated with organic substances. The ozone isnormally created in an electric arc in the form of the so-calledcorona-ozone, whereby there as a unfortunate side effect is created NOX,which is damaging the environment and health injuring to human beings.

In other cases different chemicals for decomposing and destroying theorganic substances are added to the contaminated air. The chemicals can,however, themselves contribute to contamination of the air, and the sameapplies to those products which are created by the chemical reactionspurifying the air.

SUMMARY OF THE INVENTION

The object of the invention is to provide a procedure of the typementioned in the opening paragraph, which is capable of eliminating theproblems connected to the currently available methods for removal of theorganic substances and/or foul smell in the contaminated air.

The novelty and uniqueness of the invention, that the contaminated airis set into a streaming condition; that the created air stream isbrought to change direction at least once; that the air stream is cooledoff; that secondary air and/or oxygen is added to the air stream; thatthe air stream is radiated with ultra-violet light; that the aircontinues to stream for a predetermined interval of time; and that theair stream is let out into the surroundings.

Organic substances in the form of larger particles are initiallyseparated by this method at that stage where the air stream changesdirection. Then the air is relieved of particles, which otherwise couldrestrain the processes in the succeeding process steps.

By cooling off contaminated air, which derives from a hot continuousprocess, it is attained that water in the form of saturated vapour andorganic substance condensate and thereby separate the air released fromthese vapours more easily can be processed in the succeeding steps ofthe process.

The oxygen supplied in the form of the oxygen content in a secondary airstream or as pure oxygen serves the sole purpose of securing, that thecontaminated air sufficiently is provided with oxygen to create ozone tothe necessary extent, when the air is radiated with the ultra-violetlight. Since the ozone is created at a low temperature and by means ofultra-violet light, no secondary product, as previously mentioned, inthe form of dangerous NOX created by corona effect, will emerge.

Certain organic substances are oxidized by the ozone in a so-called coldcombustion and are thereby transformed into carbon dioxide, but manyorganic molecules can not be oxidized in this way. The ultra-violetlight, which radiates the oxygen molecules and thereby creates ozone,will, however, at the same time influence the organic substances with aphoto light effect, which splits the organic molecules, which normallywould be difficult for the ozone to oxidize into molecules more easy tooxidize by ozone. Thereby is obtained that it is possible to oxidize alarger amount of the content of organic substances in the contaminatedair than by means of ozone alone.

The oxidation process does not occur instantaneously, and therefore theair stream is brought to continue as long as the oxidation process ofthe organic substances takes, before the purified air is being releasedinto e.g. the open air.

When the contaminated air is warmer than the supplied secondary airand/or oxygen, this secondary air advantageously can be used for coolingoff the air, before it is radiated by the ultra-violet light.

Furthermore the best effect is obtained by using short wavelengthultra-violet light for the radiation.

The invention also concerns a filter device for removing and/ordestroying organic substances in contaminated air, which comprises ahouse and a least one ventilator for sending the air stream through thehouse, in which there, in open connection with each other are; a firstchamber with an opening, which is connected to a source of contaminatedair; a second chamber with a number of metal sheets placed across themain direction of the air current which sheets are to bring the aircurrent to change direction at least one time; a third chamber with anumber of perforated tubes, as in secondary air source; a fourth chamberwith a number of lamps for radiating the air current with ultra-violetlight and; a fifth chamber with a volume allowing the air current, atpredetermined interval of time, to stay in the chamber, and which has anopening through which the purified air is released to the surroundings.

By means of this construction the procedure according to the inventioncan be carried through efficiently and economically. The chambers can,for example, be built vertically on top of each other with the fifthchamber at the top. The air current, which is generated by theventilator, is then successively passing the various chambers andthereby run through the processes which finally result in purified airbeing released into open air.

The ventilator can in principle be inserted any place at all in the aircurrent, but it is most expedient to place the ventilator after thefifth chamber and connect its opening with the suction side of theventilator.

The air passing through the ventilator is thereby purified air only,which prevents the build-up of a coating of organic substances fromcontaminated air in the ventilator, which would reduce the efficiency ofthe ventilator.

From the source of contamination the contaminated air streams into thefirst chamber via its inlet. It is important that the air is distributedequally in the succeeding chambers for the processes to run at theiroptimum. For this purpose, according to the invention, there canadvantageously be placed one or more distribution sheets in the firstchamber, preferably somewhere behind the inlet opening of the air.

In the second chamber the air is met by a number of de-cindering sheetsforcing the air to sudden change of direction at least one time. Therebyorganic particles and water drops are removed from the air.

The sheets are by an expedient embodiment placed in at least two rowsacross the main direction of the air current in such a way, that thesheets in each row are placed at a mutual interval, and each interval isplaced opposite a sheet in the adjoining row.

The lamps for radiating the air, which streams through the fourthchamber, with short wavelength ultra-violet light, can according to theinvention be high pressure U.V. lamps and/or low pressure U.V. lamps.Such lamps work best at a temperature of approximately 38° C., and it istherefore necessary to cool the air before radiation, if the suppliedair has a temperature, which is higher than 38° C., such as it often isthe case within, for example, the food industry.

With one embodiment an electric evaporator can be inserted in access tothe fourth chamber, for example, to cool the air.

This construction is especially expedient when the contaminated air isadded to the filter device at a high temperature.

A second embodiment suitable for cooling contaminated air with lowertemperatures, the secondary air can function as a cooling device. Thecontaminated air is then brought to circulate abeam of the perforatedtubes, while the secondary air is sucked in along the tubes having itsholes place on the lee side. The two air currents are mixed, when thesecondary air streams out of the holes in the perforated tube. Duringthis process the secondary air cools off the perforated tubes, whichagain cool off the contaminated air.

By cooling off the contaminated air, is obtained, as mentioned before,that the temperature of the air is adjusted to the most suitable levelfor the the ultra-violet lamps to function at its optimum. Anotheradvantage is obtained by a reduction of the humidity of the air, as apart of the aqueous vapour in the air condense on the tubes and leavesthe house via drain pipes herein.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be explained more fully in the following descriptionof embodiment which just serves as example, with reference to thedrawing, where

FIG. 1 schematically shows, seen from the side, partly sectional, afilter device according to the invention adapted for de-sucktion andpurification of contaminated air from an industrial deep-fat fryer forpreparation of a foodstuff product,

FIG. 2 shows the same, seen from the end,

FIG. 3 shows in a large scale, seen from the side, a section through thefilter device shown in FIGS. 1 and 2, and

FIG. 4 shows the same, seen from the end.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIGS. 1 and 2 show a filter device according to the invention, which ingeneral is indicated by the reference number 1. In this case of example,the filter device serves the purpose of removing air contaminated withespecially dripping by industrial preparation of a foodstuff in adeep-fat fryer, which in general is indicated by the reference number 2.

The deep-fat fryer is shaped as a big oblong basin 3, which is filledwith hot dripping 4, serving the purpose of frying a foodstuff product5, which is divided into pieces. The single pieces 5 are in the processplaced on an endless wandering grill 6 transporting the product throughthe deep-fat fryer in submerged condition.

The deep-fat fryer stands with legs 7 on a underlayer 8, e.g. a plantfloor. Above the deep-fat fryer is placed a range hood 9, which isconnected to the filter device 1 via an air duct 10, (FIG. 2). The rangehood collects vapours and particles from the deep-fat frying, especiallyfat and water vapours.

These vapours and particles are successively sucked from the range hoodvia the air duct 10, the filter device 1, and a second air duct 11,which is connected to the suction side of a ventilator 12, which isplaced on the roof 13 of the production premises and serves the purposeof releasing the purified air into the open.

In FIGS. 3 and 4 are shown the filter device 1 side view and from theend in a cross section, respectively. The filter device comprises fivechambers placed vertically on top of each other, namely a first chamber14, a second chamber 15, a third chamber 16, a fourth chamber 17 and afifth chamber 18. The chambers are in open connection with each other,and the first chamber 14 is furthermore connected to the range hood 9via the first air duct 10, while the fifth chamber 18 is connected tothe ventilator 12 via the second air duct 11.

When the ventilator is on, it drives a stream of contaminated air fromthe process in the deep-fat fryer 2 through the five chambers 14-18 inthe direction indicated by the arrows, whereby the air successively ispurified as described in details in the following.

The first chamber 14 is a distribution chamber, in which the air isevenly distributed before it is released into the succeeding chamber 15.In order to obtain an even distribution a distribution sheet 19 isplaced somewhere before the outlet of the air duct 10 in the firstchamber.

In the second chamber 15 there are placed two rows of sheets 20, whichare displaced in relation to each other. Each sheet has along the twoopposite sides a folded flap 21, and the flaps in the one row arefurthermore turning towards the sheets in the other. When the air isstreaming through the sheet rows, it will consequently be forced toseveral sudden changes of direction, whereby particulate matter andwater are separated from the air and removed via drain ducts (notshown).

In the third chamber 16 there is transverse to the air stream placed anumber of quadrangular tubes 22, extending between two of the oppositewalls 23 of the chamber. The tubes 22 are tightly connected to thesewalls 23 and end in, as shown, an inlet duct 24 on each side of thethird chamber 16. In each inlet duct 24 is placed a distribution sheet25 for distribution of the air let in through the duct 24. Furthermore agate 26 is placed for optional close of the duct in question or throttledown the through flow. The quadrangular tubes 22 are at the lee side ofthe contaminated air stream perforated with a number of rather smallholes 27.

At the lee side of the quadrangular tubes 22 a partial vacuum emergeswhen the contaminated air streams by. As a result of this partialvacuum, secondary air is via the inlet ducts 24 in the direction of thearrows from an air source, e.g. the surrounding air, sucked in throughthe quadrangular tubes 22. The secondary air is even distributed overthe mouths of these tubes due to the presence of the distribution sheet25. The air is let out of the holes 27 in the tubes and is thereby mixedsmoothly with the passing contaminated air.

The secondary air cools during the passage the quadrangular tubes 22,which again cool the contaminated air, the temperature of which therebycan be lowered to a temperature suitable for the process in thesucceeding fourth chamber 17. A part of the content of aqueous vapoursin the air will at the same time condense on the tubes and be removedvia drain ducts (not shown). Thereby the humidity of the air ispreferably reduced.

In the present case the tubes 22 are quadrangular. This is, however,only to be understood as an example, since the tubes can have any othersuitable shape, e.g. round or triangular. They can also be pointed inthe longitudinal direction towards the centre to ensure an even outletof secondary air through the holes 27, and for the same reason thediameter of these holes can decrease towards the centre.

Instead of or as a supplement to the cooling, which thus takes place bymeans of the secondary air, an evaporator can be inserted, e.g. anelectrical evaporator (not shown) before the fourth chamber 17.

Besides, as mentioned, having the effect as a cooling means thesecondary flow of air and/or oxygen enriches the contaminated air, whenthe two air streams blended. As secondary air, e.g. the air which is inthe production premises can be used, but in some cases pure oxygen canbe advantageous to use, either alone or as a supplement to atmosphericalair. The fact, that the contaminated air thus is enriched with oxygen isof great importance to the process in the succeeding fourth chamber 17.

In this chamber is placed a number of lamps 28 for radiating the passingair with short wavelength ultra-violet light. The lamps 28 arehigh-pressure U.V. lamps and/or low-pressure U.V. lamps or a combinationof these types of lamps. The most efficient working temperature of thelamps is approximately 38° C., and that is the reason for cooling theair in the preceding chamber 16 down to or near this temperature in thecases, where the air from the production process had a highertemperature than 38° C., as it often will be the case within thefoodstuff industry, e.g. by deep-fat frying.

The lamps 28 are connected to a suitable current source (not shown) bymeans of electrical connections 29, which are well protected fromexterior influence behind screens 30.

When the oxygen of the oxygen-enriched air is radiated with the shortwavelength ultra-violet light, the oxygen is transformed, or at leastpart of it, into ozone at such a low temperature that there to nosubstantial extent is a risk for creation of NOX.

The large content of oxygen of the oxygen-enriched air results in thefact that substantial amounts of ozone are created, and ozone is, aswell-known, capable of oxidizing organic substances in a so-calledcold-combustion and convert the substances into carbon dioxide. Manyorganic molecules will, however, not be oxidized straight away in thisway, but the ultra-violet light also serves the purpose of creating aphoto light effect to split the difficult oxidizable molecules tomolecules, which more easy can be oxidized by the ozone. The effect ofthe cold combustion is therefore multiplied many times compared to theresults that can be obtained by conventional cold combustions usingozone only.

After the radiation in the fourth chamber 17, air stream into the fifthchamber 18, which is dimensioned with such a large volume, that the coldcombustion will have time finish before the purified air is releasedinto the open air via the second air duct 11 and the ventilator 12.

The method and the filter device according to the invention is extremelyefficient to purify contaminated air from organic substances without useof chemicals and physical filters, such as fat and carbon filters. Thefilter device is hygienic and fireproof, since its interior surface isnot being covered with organic materials. The releasing tubes and theventilator are furthermore easy to clean. For the purpose of cleaningall that is needed is a broom since the remnants of the de-contaminationprocess consist of dust.

The above-mentioned described and in the drawings shown filter device isonly an example of the way a filter device according to the inventioncan be constructed.

The filter device can, however, be made in many other ways. Thus can thechambers be placed horizontally or diagonally instead of vertically ontop of each other, and the chambers do not have to be build directlytogether, but can be mutually connected via air ducts.

What is claimed is:
 1. Method for removal and/or destruction of organicsubstances in contaminated air, characterized in that it comprises thefollowing successive process steps: a. that the air is brought into astreaming condition; b. that the air stream created is brought to changedirection at least one time in such a way that solid particles which areentrained in the contaminated air stream are removed; c. that the airstream is being cooled such that water and organic substances being inthe vapour phase in the contaminated air are condensed and subsequentlyremoved from the air stream; d. that the air stream is supplied with asecondary flow of air and/or oxygen; e. that the air stream is radiatedwith ultra-violet light, such that the supplied oxygen forms ozone insitu for oxidizing the organic substances into carbon oxides at asufficiently low temperature to avoid undesirable radiation byproducts;f. that the air stream continues for a predetermined interval of time;and g. that the air stream is released.
 2. Method for removal and/ordestruction of organic substances in contaminated air according to claim1, characterized in that the air stream is cooled by the secondary flowof air and/or oxygen.
 3. Method for removal and/or destruction oforganic substances in contaminated air according to claim 1,characterized in that the air stream is radiated with short wavelengthultra-violet light.
 4. A filter device for removal and/or destruction oforganic substances in contaminated air, having a housing and at leastone ventilator for sending an air stream through the housing, whichfilter device comprises: a. a first chamber with an opening, which isconnected to a source for a contaminated air stream; b. a second chamberwith a number of sheets placed transversely to the main direction of theair stream for making the air stream change direction at least one timein such a way that solid particles which are entrained in thecontaminated air stream are removed; c. a third chamber with a number ofperforated tubes which, at least at one end, are in open connection witha secondary air source having oxygen which has a lower temperature thanthe contaminated air stream to thereby cool the air stream, such thatwater and organic substances in the vapour phase in the contaminated airare condensed and subsequently removed from the air stream; d. a fourthchamber with a number of UV lamps for radiating the air stream withultra-violet light such that the supplied oxygen forms ozone in situ foroxidizing the organic substances into carbon oxides at a sufficientlylow temperature to avoid undesirable reaction byproducts; e. a fifthchamber of a volume, which allows the air stream to stay for apredetermined interval of time in the chamber, and which has an opening,through which purified air is released; wherein each chamber isconnected to the next in succession.
 5. A filter device for removaland/or destruction of organic substances in contaminated air accordingto claim 4, characterized in that there in the first chamber is placedat least one sheet for distribution of the stream of contaminated air.6. A filter device for removal and/or destruction of organic substancesin contaminated air according to claim 4, characterized in that there,in the second chamber transversely to the main direction of the airstream, are placed at least two rows of sheets, that the sheets in eachrow are placed at a mutual distance, and that each sheet is placedopposite a sheet in the adjoining row.
 7. A filter device for removaland/or destruction of organic substances in contaminated air accordingto claim 4, characterized in that each perforated tube of the thirdchamber extends transversely to the main direction of the air stream,that each tube is open at least in one end, that this end extendsthrough one of the walls of the chamber, and that the holes in the tubesare placed on the lee side.
 8. A filter device for removal and/ordestruction of organic substances in contaminated air according to claim4, comprising an electric evaporator before the fourth chamber.
 9. Afilter device for removal and/or destruction of organic substances incontaminated air according to claim 4, characterized in that lamps inthe fourth chamber are high-pressure UV lamps and/or low-pressure UVlamps for emission of short-wavelength ultra-violet light within apredetermined spectrum.
 10. A filter device for removal and/ordestruction of organic substances in contaminated air according to claim4, characterized in that the ventilator is connected to the opening ofthe fifth chamber.
 11. A method for removing and/or destroying organicsubstances in contaminated air, successively comprising: bringing thecontaminated air having a plurality of solid particles into a streamingcondition for a predetermined interval of time to create a contaminatedair stream in a device; changing the direction of the contaminated airstream at least one time in a way sufficient to remove solid particlesentrained in the contaminated air stream; supplying the contaminated airstream with a secondary flow of air and/or oxygen sufficient to impartcooling of the contaminated air stream to condense water and organicsubstances in the vapor phase to remove them from the air stream;irradiating the contaminated air stream within a treatment zone withultra-violet light such that ozone is created in situ from the suppliedsecondary flow to oxidize the organic substances into carbon oxides at asufficiently low temperature to avoid undesirable radiation byproducts,thereby decontaminating the air stream; and releasing the decontaminatedair stream from the device.
 12. The method of claim 11, wherein theirradiating comprises applying short-wavelength ultra-violet light.